Photoelectric tube



Aug. l7, 1937. P. GRLICH 2,090,387

FHOTOELECTRIC TUBE Y Filed March 30, 1956 www Patented Aug. 17, 1937 PATENT OFFICE PHOTOELECTRIC TUBE Paul Grlich, Dresden, Germany, assigner to Zeiss Ikon Aktiengesellschaft, Dresden, Germany Application March 30, 1936, Serial No. 71,560 In Germany August 9, 1935 1 Claim.

The invention relates to improvements in photoelectric tubes and particularly pertains to a novel construction of a tube of this type which is adapted to make full use of the action of the 5 secondary emission of electrons.

It is an object of the invention to substantially increase the emission of electrons of a photoelectric tube by causing the electrons emitted by the primary cathode due to incident light to impinge with suiiicient speed upon a secondary cathode, which then emits substantially more electrons than have been received by the same.

The drawing illustrates various embodiments of the photoelectric tube of the present invention.

Fig. 1 is a horizontal cross-sectional View, of a photoelectric tube which shows the arrangement of the electrodes, and

Fig. 2 is an elevation View of the photoelectric 2O lCube.

As shown in the Figs. l and 2, a cylindrically shaped vessel l is provided on lone portion of its interior wall with a primary cathode 2. Opposite this cathode 2 is positioned a secondary cathode 3. This secondary cathode 3 is provided with a window 4 through which the light rays may enter the tube as indicated by the arrows in Fig. l.

An anode E is arranged in the center of the vessel between the primary cathode 2 and the secondary cathode 3. According to Fig. l, the anode 5 consists of a screen of tubular shape.

The cathodes arranged in the vessel I, namely the primary cathode 2 and the secondary cathode 3, preferably are formed in such a way that the electrons leave the surfaces very readily. In

other words, the cathodes should have a low emitting power. Such a low emitting power may be obtained incustomary manner by providing the metallic base with a coating of an alkali metal or a metal of the alkaline earths, particularly caesium. A still lower emitting power is ob- (Cl. Z-27.5)

tained when the above mentioned metals are deposited upon a base covered with oxide. While both cathodes 2 and 3 may be provided with such coatings, it is also possible to provide only one of the two with such a coating, depending upon the purpose for which the photoelectric tube is to be used.

The screen anode has the advantage that the shadow thrown upon the primary cathode is less and yet a large surface for receiving the secondary electrons is formed.

The photoelectric tube of the present invention permits a great amplication of the primarily produced current of electrons. A particular advantage resides therein but this photoelectric tube operates independent of frequency, so that it is possible, for instance, to employ with sound films a photoelectric tube of this type having an evacuated vessel without a gas lling.

When this photoelectric tube is used for television and sound nlm purposes, the number of amplication stages may be reduced, which is another substantial advantage.

In order to produce still larger photoelectric currents the vessel of the photoelectric tube may be lled with a gas under any desired pressure. If an alkali metal or a metal of the alkaline earths has been used to reduce the emitting power it is recommended to employ a filling of rare gas, for instance argon or a rare gas mixture.

What I claim as my invention is:

A photoelectric tube, including within a cylindrical vessel, an anode consisting of a screen in the center of said vessel, a primary cathode on one side of said anode and attached to the inner cylindrical Wall of said vessel, and an arcuate secondary cathode mounted diametrically oppo. site said primary cathode and radially spaced from said anode, said secondary cathode having a window to admit light to said primary cathode.

PAUL GRLICH. 

